martin rudalics writes:
 > 
 > Thanks.  According to that dump you should see the minibuffer.

Definitely no minibuffer, I had to do the M-: commands very carefully
as I couldn't see what I was typing!

> What
 > does evaluating
 > 
 > M-: (frame-parameter nil 'minibuffer)

Unfortunately after Juanma's suggested change (and then reverting it
and an emacs restart) I get the frame *with* a minibuffer but without
the window decorations.

When that command gives me:

#<window 4 on  *Minibuf-0*>

but that is probably not relevant in the new situation
> 
 > give?  The fact that no title bar is visible is even more strange.  Do
 > you see menu bar and scroll bar normally?  Post your screenshot, it's
 > simpler than telling details.

(sorry I wasn't sure if you needed to do something special to
associate an image with a bug report, I'm just attaching it to the
email) I'm attaching the screenshot together with a normal emacs frame
for comparison